The Senate Races 17 September 2016

There has now been polling in Arizona and John McCain looks comfortably in control. The changes this week that have made the most difference are in New Hampshire, where incumbent Kelly Ayotte has become the favorite, and Missouri, where Roy Blount's re-election in no longer a sure thing. 

Here are the changes from last week.

Probability of Republicans holding the Senate outright: 54.3%, up from 45.5%
Probability of a 50-50 split: 29.4% down from 34.2%
Probability of the Democrats taking the Senate back: 16.4%, down from 20.1%

Races that look close.
1. In Pennsylvania, GOP incumbent Pat Toomey was trailing challenger Katie McGinty in August, but is now in a flat-footed tie at 50% to 50%. These numbers are the same as last week's.

2. A surprising poll in Missouri says Jason Kander is now in a race with one term senator Roy Blount. Articles are crediting Kander's ad in which he assembles a firearm blindfolded, one of those valuable skills every senator from Missouri needs, I suppose. The odds right now are 57% to 43% in favor of Blount. Prior to this week it was about 91% to 9% in Blount's favor.

3. Nevada is next closest and it favors the Republican Joe Heck over Democrat Catherine Cortez Masto, vying for the seat being vacated by Harry Reid. This would be a gain for the GOP. The probabilities of victory in an election held today are 72% for Heck and 28% for Cortez Masto, which is a gain for Heck over last week's 56% to 44% numbers.

4. New Hampshire is the third closest and Kelly Ayotte has pulled ahead of her Democratic challenger Maggie Hassan. The odds here are 72% to 28%, respectively. This change is the biggest reason for the overall improvement in the Republican chances in the upper chamber.

5. In Indiana, incumbent Todd Young leads trails challenger Evan Bayh. This would be a loss of a seat for the GOP. The current odds are 14% to 86%, respectively, unchanged from last week.

6. In North Carolina, incumbent Richard Burr leads challenger Deborah Ross. This would be a hold of a seat for the GOP, so no net gain. The current odds are 87% to 13%, also unchanged from last week.

7. In Wisconsin, Russ Feingold is a solid favorite to beat Ron Johnson at 89% to 11%. This would be a gain for the Democrats, and the number is yet again unchanged for last week.

These races would say the Republicans are most likely to lose three or maybe four seats, which would put them at either 51 or 50 seats, as shown in the line graph above. I have set 95% as the arbitrary mark for a solid lead, but in my experience it's the races that are closer than 75% to 25% that are actually contests in doubt. Pennsylvania, Missouri, Nevada and New Hampshire would count by that standard.

Back tomorrow with the numbers in the presidential race.